The present invention relates to a new and improved construction of gas-blast switch.
In its more particular aspects, the present invention specifically relates to a new and improved construction of a gas-blast switch comprising a moveable and a stationary contact element, both of which are substantially tube-shaped or tubularly constructed. A blast nozzle is associated in a fixed reference position with respect to one of the contact elements and the narrowest location or throat of the blast nozzle is positioned forwardly of this contact element and is closed by the other contact element in a cut-on position of the gas-blast switch. The blast nozzle has an inlet which communicates, during a cut-off stroke of the gas-blast switch, with a pressurizable pump space or chamber bounded by a cylinder and a piston through which displaceably extends the one contact element with which the blast nozzle is associated. Both the contact elements are provided in related regions which are remote from their free ends with related outlets which interconnect an interior space formed in the related contact element and a blow-out space in a cut-off position of the gas-blast switch.
In a gas-blast switch of such type as known, for example, from Swiss Patent No. 587,556, published on May 13, 1977, there starts, during the cut-off stroke and immediately after the contact elements have been separated from each other, an axially directed flow-off of the extinguishing gas, which is strongly heated by the arc and subjected to additional pressure, through the two contact elements into the blow-out space. Particularly during the cut-off of strong currents the additionally pressurized extinguishing gas retroacts on the pump space, whereby very high pressure peaks occur which have to be overcome at any rate by the drive means for the gas-blast switch. Therefore, the drive means in the known gas-blast switch have to be powerfully and massively constructed such that a faultless movement of the contact elements is also ensured during the cut-off of very strong currents.
Other constructions of gas-blast switches have been disclosed in the commonly assigned Swiss Patent No. 568,649, published Oct. 31, 1975 and Swiss Patent No. 570,694, published Dec. 15, 1975.